With the growing concern over global climate change as well as oil supplies, there has been a recent trend to develop various hybrid systems for motor vehicles. While numerous hybrid systems have been proposed, each system typically requires significant modifications to the drive train of the corresponding vehicle. These modifications make it difficult to retrofit the systems to existing vehicles. Moreover, some of these systems have a tendency to cause significant power loss, which in turn hurts the fuel economy for the vehicle. Thus, there is a need for improvement in this field.
One of the areas for improvement of hybrid transmissions is in the construction and arrangement of the hydraulic system. Hybrid vehicles, and in particular the hybrid transmission module associated with such a vehicle, have various lubrication and cooling needs which depend on engine conditions and operational modes. In order to address these needs, oil is delivered by at least one hydraulic pump. The operation of each hydraulic pump is controlled, based in part on the lubrication and cooling needs and based in part on the prioritizing when two hydraulic pumps are included as part of the hydraulic system of the hybrid vehicle. The prioritizing between hydraulic pumps (mechanical and electrical) is based in part on the needs and based in part on the operational state or mode of the hybrid vehicle.